1. Technical Field
The present invention relates to electro-optical apparatuses, and in particular relates to a transflective electro-optical apparatus capable of reflective display by reflecting incident light from an observing side as well as capable of transmissive display by transmitting incident light from a back face.
2. Related Art
A transflective liquid crystal device, which is a kind of electro-optical apparatus, includes a transflective layer that transmits light from a backlight located between a liquid crystal layer and a backlight unit, and also reflects external light. This transflective layer includes at least one opening for transmitting light from the backlight. The transflective layer also includes an uneven reflection surface for diffusing external light so as to prevent an observer from being mirrored on the screen.
A method for making the uneven reflection surface is described in Japanese Unexamined Patent Application Publication No. 2003-75987, for example. In this method, as shown in FIG. 14(a), a substrate 500 is coated with a positive photosensitive resin 510, and the applied photosensitive material is exposed to light using a photo-mask 520. Light-transmission parts 530 randomly arranged in the photo-mask 520 are for making an uneven surface on an underlying film 540a. When a photosensitive resin is developed after being exposed to light with such a photo-mask 520, the underlying film 540a having an uneven surface shown in FIG. 14(c) is made. Then, after the underlying film 540a is post-baked, the positive photosensitive resin is again applied on the as-formed uneven surface and the substrate 500 so as to expose a mounting region around a panel display area to light. When the photosensitive resin is developed after being exposed to light, the underlying film 540b having an uneven surface shown in FIG. 14(d) is made. After the underlying film 540a and the underlying film 540b are post-baked, a reflection layer 560 is formed by depositing a material with light reflectivity, such as aluminum, only on the uneven surfaces of the underlying films.
In the method disclosed in Publication No. 2003-75987, a series of processes (“application of a photosensitive resin, exposure to light, development, and post-baking”) are performed twice to make the reflection layer 560. When the number of the processes is large like this, manufacturing takes a long time which increases manufacturing cost. In order to reduce the manufacturing period and cost, a method may be applied to eliminate the secondary series. In this case, the reflection layer 560 is formed on the substrate 500 and an underlying film 540a made in the first series. However, with only the first series, as shown in FIG. 14(c), since the bottom of concave portions of the underlying film 540a reaches the substrate, if the reflection layer is made as it is, the reflection layer reaching the bottom of the concave portions becomes flat, so that excellent scattering characteristics cannot be obtained. To prevent the reflection layer formed on the bottom of the concave portions from being flat, a method may be applied wherein the exposure is executed so that the bottoms of the concave portions do not reach the substrate. Specifically, in the exposure process, illumination of light is controlled so that the depth of the photosensitive material, through which light acts, is smaller than the film thickness of the photosensitive material. When development is performed after such exposure, the underlying film is made with concave portions that are shallower than the film thickness of the photosensitive resin. However, in such a manner, since the light acting on the photosensitive material does not act all the way to the bottom of the substrate, some photosensitive resin is left on a portion outside of the uneven surface, i.e., a portion outside of a panel display area. If the resin is left on a portion corresponding to a mounting region outside of the panel display area, a problem arises in that a data line made of a light-transmission conductive material, such as ITO (indium tin oxide), and provided in this region is broken.
The present invention has been made with such problems as a background, and it is an object of the invention to provide a manufacturing method of an electro-optical apparatus substrate, a manufacturing method of an electro-optical apparatus including the manufacturing method of the electro-optical apparatus substrate, the electro-optical apparatus substrate, the electro-optical apparatus using the electro-optical apparatus substrate, and an electronic instrument, which are capable of removing a photosensitive resin formed on an uneven portion to a depth smaller than the film thickness of the photosensitive resin while not leaving the photosensitive resin on portions other than the uneven portion.